Anyone no the place to buy the small o-ring in the fill valve on a hw100 it go's behind the screw that's behind the air gauge I just had one for repair I gave it a clean as there was some dirt around it "im hoping this caused the leak" the seal kits I have seen don't seen to show the o-ring in question it has a very small brass centre I thought it was just a normal o ring with a collect in the middle but it seems to be all one piece --the cylinder now seems to be holding air it passed the bath test with no bubbles finger crossed that's it ---I think these are well made but over engineered guns why not keep things simple